add mlockall and munlockall

CHANGELOG.md

@@ -6,6 +6,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased]
 
 ### Added
+- Added `mlockall` and `munlockall`
+  ([#876](https://github.com/nix-rust/nix/pull/876))
 - Added `SO_MARK` on Linux.
 - ([#873](https://github.com/nix-rust/nix/pull/873))
 - Added `getsid` in `::nix::unistd`

src/sys/mman.rs

@@ -205,14 +205,39 @@ libc_bitflags!{
     }
 }
 
+libc_bitflags!{
+    /// Flags for `mlockall`.
+    pub struct MlockAllFlags: c_int {
+        /// Lock pages that are currently mapped into the address space of the process.
+        MCL_CURRENT;
+        /// Lock pages which will become mapped into the address space of the process in the future.
+        MCL_FUTURE;
+    }
+}
+
+/// Locks all memory pages that contain part of the address range with `length` bytes starting at
+/// `addr`. Locked pages never move to the swap area.
 pub unsafe fn mlock(addr: *const c_void, length: size_t) -> Result<()> {
     Errno::result(libc::mlock(addr, length)).map(drop)
 }
 
+/// Unlocks all memory pages that contain part of the address range with `length` bytes starting at
+/// `addr`.
 pub unsafe fn munlock(addr: *const c_void, length: size_t) -> Result<()> {
     Errno::result(libc::munlock(addr, length)).map(drop)
 }
 
+/// Locks all memory pages mapped into this process' address space. Locked pages never move to the
+/// swap area.
+pub fn mlockall(flags: MlockAllFlags) -> Result<()> {
+    unsafe { Errno::result(libc::mlockall(flags.bits())) }.map(drop)
+}
+
+/// Unlocks all memory pages mapped into this process' address space.
+pub fn munlockall() -> Result<()> {
+    unsafe { Errno::result(libc::munlockall()) }.map(drop)
+}
+
 /// Calls to mmap are inherently unsafe, so they must be made in an unsafe block. Typically
 /// a higher-level abstraction will hide the unsafe interactions with the mmap'd region.
 pub unsafe fn mmap(addr: *mut c_void, length: size_t, prot: ProtFlags, flags: MapFlags, fd: RawFd, offset: off_t) -> Result<*mut c_void> {